A wide variety of apparatus is known for inverting stacks of sheets of corrugated paperboard. For example, see U.S. Pat. Nos. 2,776,831; 3,422,969; 3,643,939; 3,885,781; 3,982,750; 4,022,322; and 4,042,234. The lifting device in each of said patents is generally L-shaped and is operated by a cylinder or other motor for pivotable movement whereby it oscillates from a loading position to a delivery position. The generally L-shaped devices in said patents oscillate back and forth and constitute a potential safety hazard to personnel. The present invention is directed to a solution of the problem of how to increase safety.